.#{$baseSelector}background {
    @extend .w-100-p,.min-h-100-vh,.h-100-p; 
    background: $backgroundBgColor;
    .#{$baseSelector}wrapper{
        @extend .w-100-p,.flex-center,.el-fd-column;
        .#{$baseSelector}container {
            @extend .el-pos-r,.w-100-p;
            @media only screen and (min-width:$mediaMinWidth) {
               // cannot use @extend syntax across media queries
               // use the mixin syntax
               & { @include w(960,px); }
            }
        }  
    }
}